FIG. 2.

Schematic representation of the Nostoc sp. strain PCC 7120 hox gene clusters and the regulatory promoter regions of the two operons. Positions of the DNA probes used for Northern blot hybridizations (Fig. 3) and DNA fragments used in EMSAs (Fig. 5 and 6) are depicted as lines above the respective maps. The identified TSPs are indicated by arrows and depicted in boldface and underlined in the sequence. Putative −10 and −35 regulating sequences are underlined, and the segments of 40 nucleotides that show a high degree of homology in the two promoter regions of alr0750 and hoxU are indicated with the matching nucleotides shown in lowercase. The ribosomal binding site is shown in italics, and the start codons of hoxE (A), hoxU (B), and alr0760 (C) are shown in boldface and italics. The putative LexA binding sites are indicated with a white box in the map and depicted in boldface in the sequences. In addition, the suggested consensus LexA binding sites (11, 27) are shown above the Nostoc sp. strain PCC 7120 sequences.